Saturday, March 03, 2007

Above: visible appearance of a typical deposit of dangerous fallout; this is a secret photo from WT-1317 of a fallout tray automatically exposed for just 15 minutes at 1 hour after detonation of the 3.53 megaton, 15% fission surface burst Redwing-Zuni at Bikini in 1956. The fallout illustrated occurred on barge YFNB 13, located 20 km North-North-West of ground zero (downwind). The circular tray’s inner diameter is 8.1 cm. This 15 minute sample is only 22% of the total deposit of 21.9 g/m2 which occurred at that location. The barge’s radiation meter recorded a peak gamma intensity of 6 R/hr at 1.25 hours after the explosion.

Because fallout sinks in the ocean (which shields the fallout quite effectively, giving only a small dose rate) and the barge deck is much smaller than a land area, the barge radiation meters record only about 25% of those on land which are contaminated to the same extent. So on land the peak gamma ray intensity for this fallout would have been 4 x 6 = 24 R/hr at 1.25 hours. Correcting from 15% fission yield to 100% fission yield would increase this to 160 R/hr. The infinite time fallout dose is 5 times the peak intensity times the time of that intensity as measured from the time of explosion. Hence the infinite dose outdoors on land for pure fission would be 5 x 160 x 1.25 = 1000 R which is lethal. Any house would provide enough protection to save your life, however. (The dose law of 5 times intensity times arrival time is based on the t-1.2 decay law. Obviously it is well known that the fallout intensity drops below that law within 200 days, and a better law is 4 times intensity times arrival time. On the other hand, some radiation is received before the peak dose rate occurs, so it is sensible to use the factor of 5 multiplication as a rough approximation.)

Above: Dr Carl F. Miller’s correlation of measurements of the decay rates of fallout from different tests during Operation Castle, 1954. (Dr Miller’s own U.S. Naval Radiological Defense Laboratory report on these decay rate correlations has never been declassified, and even in one of his major fallout reports which is now declassified, some of the statistics are blanked out because they are still secret. Part of the trouble is that the neutron capture to fission ratio in the uranium-238 component of a hydrogen bomb produces substantial quantities of nuclides like Np-239, U-237, etc., which affect the decay rate of the subsequent fallout. Therefore there is a link between the highly classified thermonuclear design physics and the radioactive hazards.)

Above: Cresson Kearny explains how to shield against fallout by making a ‘core shelter’ inside a building: put cardboard boxes on top of, and around, a strong table that you can shelter under: then put two large waterproof plastic waste bags inside one another in each box, and simply fill them up with water. This saves you messing around with dirt for shielding. Just 5 inches of water halves the intensity of 1 MeV gamma radiation penetrating it. Actually, dirty bombs with U-238 jackets produce a great deal of softer gamma rays from Np-239 (which has a half life of 56 hours and thus contributes a peak percentage to fallout radiation at a time of 1.73 X 56 = 4 days after burst) and U/Np-240, as well as U-237 which has a longer half life and contributes substantially during the two week sheltering period. So protection is even more efficient than Kearny quotes, due to the lower-energy of fallout from dirty hydrogen bombs with neutron capture in U-238. American experiments on fallout shielding by buildings used cobalt-60 gamma rays, which have a mean energy of 1.25 MeV (see page 120, ‘Transmission Factors’ in the PDF file of the U.S. Army Field Manual 3-3-1, Nuclear Contamination Avoidance, linked here) whereas dirty (high fission yield) thermonuclear weapons which contaminate large areas all expose U-238 to neutrons which always results in large amounts of non-fission neutron captures in U-238, creating large amounts of very low-energy gamma emitting Np-239, U-240, and U-237. The time that any neutron induced species contributes a peak percentage of the radiation from fallout is equal to 1.73 times its half-life (the 1.73 factor is simply the ratio 1.2/ln2, where 1.2 is the decay exponent of time for the overall mixture of nuclides in fallout, while ln2 is the factor which converts the average life of a particular nuclide into its half-life, which is always a factor 1.44 smaller than its average life). Thus, for Np-239 which has a half life of 56 hours, the peak percentage contribution it gives to fallout radiation occurs 4 days after detonation. U-237 has a half-life of 6.8 days, so contributes a peak percentage to fallout radiation 12 days after detonation.

Fractionation of fission products (the loss of slowly-condensing gaseous fission product decay chains from fast-falling large particles of fallout which exit the fireball before the slowly condensing nuclides have solidified, and are thus depleted in many fission product species) also affects the spectrum of gamma ray energy in a predictable way, softening the spectrum to lower mean energies in the close-in (depleted) fallout. Dr Terry Triffet first made this effect public in the 22-26 June 1959 U.S. Congressional Hearings on The Biological and Environmental Effects of Nuclear War, pages 61-111. Triffet in that testimony, with more details in in his declassified weapon test report WT-1317, 1961 (see also Dr Miller’s 1961 report USNRDL-466 for REDWING fallout station distances from ground zero, nuclide measured fractionation ratios and neutron induced activity data), showed that at 1 week after burst, the mean gamma ray energy of fractionated fallout 8 statute miles downwind on Bikini Lagoon barge YFNB29 due to 5.01 Mt burst 87% fission REDWING-TEWA in 1956 was just 0.25 MeV (4.5 grams per square foot of fallout was deposited there, giving a peak dose rate on the barge of 40 R/hr at 2.7 hours after burst), while at 60 statute miles on ship LST611 downwind it was 0.35 MeV (due to less depletion of high energy fission products at greater distances, a fractionation effect) where only 0.06 gram/square foot of fallout was deposited giving a peak dose rate of 0.25 R/hr at 14 hours after burst. On page 205 of those June 1959 hearings, Triffet explained:

‘I thought this might be an appropriate place to comment on the variation of the average energy. It is clear when you think of shielding, because the effectiveness of shielding depends directly on the average energy radiation from the deposited material. As I mentioned, Dr Cook at our [U.S. Naval Radiological Defense] laboratory has done quite a bit of work on this. … if induced products are important in the bomb [dirty bombs with U-238 jackets], there are a lot of radiations emanating from these, but the energy is low so it operates to reduce the average energy in this period and shielding is immensely more effective.’

You make it by taking two pieces of aluminium foil and folding them repeatedly until you have two 8-ply (8-layer) pieces of square shape and 2 inch long sides (this ensures the calibration). You hang each square in contact with the other by electrically non-conducting threads or thin non-conducting fishing line (any thin thread which has not been given anti-static treatment will do!) inside a can or jar. To get it to work you do need to have dry air inside the can (in high humidity air, you can’t charge it since the water molecules almost immediately discharge the comb before it can even charge up the foil plates, so you need to put the whole thing inside a “dry bucket” with a transparent cover, adding some heated hydroscopic gypsum from plaster or re-heated silica gel to the bottom of the can, which comes in little paper packets in the packaging of all kinds of items these days, preventing moisture damage).

The top of the can is just covered by kitchen clear plastic wrap, with a little millimetre-calibrated scale on it to measure the distance between the aluminium plates when charged. A piece of wire like a straightened paperclip poked through the plastic wrap is used to charge the foil leaves; you simply bring a hair-charged plastic comb (or some other source of static electricity like a plastic ruler rubbed in a rolled up newspaper) to the charging wire, and the plates are charged. Because similar electric charges repel, the plates then move apart from one another! As air is ionized by radiation, charged air ions move between the plates, discharging them. The speed with which the plates are discharged therefore tells you the radiation level. Simple!

The most important for emergency use (where rapid protection is desirable) are the ‘car over trench shelter’ (dig a trench the right size to drive your car over, putting the excavated earth to the sides for added shielding, then drive your car over it), “tilt up doors and earth” shelter (if your house is badly damaged, build a fallout shelter against any surviving wall of the house by putting doors against it and piling earth on top in accordance to the plans), and the “above ground door-covered shelter” (basically a trench with excavated earth piles at the sides, doors placed on top, then a layer of earth piled on top of the doors).

All these shelters can be constructed very quickly under emergency conditions (in a time of some hours, e.g., comparable to the time taken for fallout to arrive in the major danger area downwind from a large nuclear explosion). For the known energy of gamma rays from fallout including neutron induced activities with low energy gamma ray emission (Np-239, U-237, etc.), a thickness of 1 foot or 30 centimetres of packed earth (density 1.6 grams per cubic centimetre) shields 95% of fallout gamma radiation, giving an additional protective factor of about 20. A thickness of 2 feet or 60 centimetres of packed earth provides a protective factor of about 400. Caravans have a protective factor of 1.4-1.8, single storey modern bungalows have a protection factor of 5-6, while brick bungalows have a protective factor of 8-9. British brick multi-storey buildings have protection factors of 10-20, while British brick house basements have protective factors of 90-150. These figures can easily be increased by at least a factor of 2-3 by making a protected ‘inner core’ or ‘refuge’ within the building at a central point, giving additional shielding:

But measured volcanic ash ingress, measured as the ratio of mass per unit area indoors to that on the roof, was under 0.6% even with the windows open and an 11-22 km/hour wind speed (U.S. Naval Radiological Defense Laboratory report USNRDL-TR-953, 1965). The main gamma hazard is from a very big surrounding area, not from trivial fallout nearby!

‘A fission density of 1015 fissions per cubic centimeter of fallout material was assumed. Comparison of computed doses with the most recent experimental data relative to skin response to beta-energy deposition leads to the conclusion that even for fallout arrival times as early as 16.7 minutes post-detonation, no skin ulceration is expected from single particles 500 micron or less in diameter. Absorbed gamma doses calculated for one particle size (100 microns) show a beta-to-gamma ratio of about 15. Dose ratio for larger particle sizes will be smaller. Doses from arrays of fallout particles of different size distributions were computed, also, for several fallout mass deposition densities; time intervals required to accumulate doses sufficient to initiate skin lesions were calculated. These times depend strongly on the assumed fallout-particle-size distribution. Deposition densities in excess of 100 mg per square foot of the skin will cause beta burns if fallout arrival time is less than about three hours, unless the particles are relatively coarse (mean particle diameter more than 250 microns).’
Keeping the highly visible particles off the skin by wearing clothing, or removing them quickly by brushing or washing after contamination, eliminates the beta burn hazard, as demonstrated by the examples of Marshallese Islanders who washed after fallout contamination:

U.S. Congressional Hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, The Nature of Radioactive Fallout and Its Effects on Man, 27 May – 3 June 1957, pages 173-216 where Dr Gordon M. Dunning testified: ‘In the case of the Marshallese who were in the fallout from the detonation at the Pacific on March 1, 1954, most of the more heavily exposed showed some degree of skin damage, as well as about half of them showing some degree of epilation [hair loss] due to beta doses. However, none of these effects were present except in those areas where the radioactive material was in contact with the skin, i.e., the scalp, neck, bend of the elbow, between and topside of the toes. No skin damage was observed where there was a covering of even a single layer of cotton clothing. … The Marshallese were semiclothed, had moist skin, and most of them were out-of-doors during the time of fallout. Some bathed during the two-day exposure period before evacuation, but others did not; therefore, they were optimal conditions for possible beta damage. The group suffering greatest exposure [Rongelap Islanders, 175 R gamma dose from 4 hours to 2 days after burst] showed 20 percent (13 individuals) with deep lesions; 70 percent (45 individuals) superficial lesions; and 10 percent (6 individuals) no lesions. Likewise, 55 percent (35 individuals) showed some degree of epilation followed by a regrowth of hair.’ On pages 944-948, Dr Eugene P. Cronkite testified: ‘The fallout material consisted predominantly of flakes of calcium oxide resulting from the incineration of the coral [reef near Namu Island at Bikini Atoll]. Upon the flakes of calcium oxide fission products were deposited. At Rongelap Atoll the material was visible and described as snowlike. … To arrive at some physical estimate of the skin dose, an attempt must be made to add up the contributions of the penetrating gamma, the less penetrating gamma, the beta bath to which the individuals were exposed from the relatively uniform deposition of fission products in the environment, and the point contact source of fallout material deposited on the skin. By all means, the largest component of skin irradiation resulted from the spotty local deposits of fallout material on deposited surfaces of the body. To put it in reverse, the individuals who remained inside had no skin burn. It was only on those on whom the material was directly deposited on the skin that received burns. … Itching and burning of the skin occurred in 28 percent of the people on Rongelap, 20 percent of the group on Ailinginae, and 5 percent of the Americans [weather station staff exposed to fallout on Rongerik Atoll]. There were no symptoms referable to the skin in the individuals on Utirik. In addition to the itching of the skin there was burning of the eyes and lacrimation in people on Rongelap and Ailinginae. It is probable that these initial skin symptoms were due to irradiation since all individuals who experienced the initial symptoms later developed unquestioned radiation-induced skin lesions that will be described later in detail. It is possible, however, that the intensely alkaline nature of the calcium oxide [produced when the coral i.e. calcium carbonate was heated in the fireball] when dissolved in perspiration might have contributed to the initial symptoms. … Burns were caused by direct contact of the radioactive material with the skin. The perspiration as common in the tropics, the delay in decontamination and the difficulties in decontamination certainly favored the development of the skin burns. Those individuals who remained indoors or under trees during the fallout developed less severe skin burns. The children who went wading in the ocean developed fewer lesions of the feet and most of the Americans who were more aware of the dangers of the fallout, took shelter in aluminum buildings and bathed and changed clothes. Consequently they developed only very mild beta burns. Lastly, a single layer of cotton material offered almost complete protection, as was demonstrated by the fact that skin burns developed almost entirely on the exposed parts of the body.’

Dr Miller tragically died from leukemia in August 1981, four months after giving that speech, and leukemia is the form of cancer which correlates most strongly with external whole body gamma radiation exposure (thyroid tumours correlate to internal intake of radioactive iodine, which concentrates in the thyroid and irradiates it with beta particles). With most cancers, the risk of per individual without radiation is not much different from the slightly enhanced risk with significant radiation exposures, but since leukemia is both a rare cancer and so strongly dependent upon radiation dose, a person who does get leukemia after a significant dose may be more likely to have the leukemia as a result of the radiation, than for it to be coincidental. Dr Miller measured his own gamma dose to total 60 rads (cGy in tissue) received at relatively high dose rates soon after nuclear tests; this more than doubled the natural 0.5% risk of death from leukemia to over 1%. The fact that he contracted leukemia therefore implies that it was over 50% certain to be due to his gamma radiation exposure at the nuclear tests where he measured the gamma spectrum of fallout and analysed the physical nature of fallout and the decontamination effectiveness against fallout hazards. He took a calculated risk to get the vital Cold War fallout protection data, and he was unlucky. It is important not to minimise the immense human costs to such scientists and their families of acquiring the valuable direct scientific information on this important subject, which has direct relevance to the problem of weapons of mass destruction in today’s world of increasing nuclear proliferation and radiological warfare threats.

Above: the need for people to understand observed facts about fallout and its decontamination in an accident or disaster. These photographs are of children accidentally exposed to fallout from the Bravo nuclear test in 1954, before the scientific aspects of fallout prediction and radiological safety had been investigated. The photographs on the left were taken about one month after exposure; those on the right show the recovery about six months later. The beta burns to neck and feet only began to appear on 14 March, two weeks after exposure (all of the beta burns and hair loss had appeared within four weeks of exposure). Because the U.S. Atomic Energy Commission had ignorantly and prematurely announced on 11 March 1954 that the 236 contaminated Marshallese had no beta radiation burns, the word fallout gained a new political meaning as an unpleasant after effect subsequently.

Above: the table of fallout areas for measured dose rate contours in PLUMBBOB-SMOKY, 31 August 1957, Nevada, is taken from page 808 of the Hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, Congress of the United States, 86th Congress, The Biological and Environmental Effects of Nuclear War, June 22, 23, 24, 25, and 26, 1959, Part 1, U.S. Covernment Printing Office, Washington, 1959, 966 pages.

This is the first detailed model of the thermodynamics of fallout, which – as the previous post on this blog mentions – found that the fraction of the total fireball (thermal plus blast) energy which in a surface burst on Nevada sand is used to melt fallout varies from about 7.5% for a 1 kt total yield to 9.2% for 100 Mt. This agreed with an empirical observation of 3% at the Redwing-Inca 15 kt tower burst in 1956; such a tower burst would produce less than half the melted fallout that a surface burst produces (due to the decreased interaction of the fireball with the ground).

Chapter 1 of Dr Miller’s Fallout and Radiological Countermeasures begins with the experimental data, showing photographs of the fallout from every type of nuclear explosion, and describing the physical, chemical and radiological processes. Since the appearance and physical, chemical and radiological nature of actual fallout is so confusing to many people – particularly in the media and politics (who naively confuse particles of radiation with particles of fallout, and end up with complete science fiction and nonsense, a problem extending even to author Richard Rhodes who in his historical book on the tests incorrectly asserted that fallout from hydrogen bombs is consists of metallic calcium), a revised adaptation of Dr Miller’s approach will follow. This is mainly because of the declassification of other reports by Dr Miller and his colleagues ( U.S. Department of Defence reports USNRDL-374, -408, -440, -TR-208, and WT-1317), which show which nuclear tests each photograph arises from, and some additional data.

In this and each of the following photographs, the photograph on the left hand side is a picture of a 30 micron thick slice through the particle (produced by gluing the particle into plastic resin and then shaving off a thin slice). The image on the right hand side is an radioautograph, i.e., an x-ray like photo in which the source of the image is the action of beta particles from the fallout particle striking a light proofed packet of photographic film. The radioautograph shows, therefore, precisely where the fission products are distributed within each fallout particle.

Pure silicate (quartz) sand particles ejected from the crater remain liquid at temperatures below 2,950 °C, and re-solidify into insoluble glass spheres when the fireball temperature falls below 1,607 °C. Before this time, condensing fission products diffuse inside molten glass droplets, creating insoluble radioactive particles, but at later times fission products are deposited on the outside of solidified glass, giving soluble (biologically available) radioactivity. I-131 on the outer surfaces of fallout particles is in the soluble –1 oxidation state (U.S. test report WT-917). Water-soluble activity is located in an outer 0.35-micron deposit on the glass, while the soluble fraction for stomach acid (0.1 N HCl, pH4) is equivalent to a deposit 10 microns thick. The insoluble fraction of the volume equals the volume of the inner insoluble glass sphere divided into the effective total volume including the soluble outer deposit:

(4/3){Pi}*r3/[(4/3){Pi}(r + X)3] = (1 + X/r)-3,

where X is the thickness of the soluble deposit (0.35 and 10 microns respectively for water and acid) and r is the insoluble glass radius, measured in the same units. The soluble activity is:

100[1 – (1 + X/r)-3] %.

This is validated by fallout studies in 1956-7 at Australian-British nuclear tests over silicate soil. Antler gave 1.8% and 0.4% water solubility for particles of average radius 75 and 200 microns, respectively. At Mosiac, activity in particles of 1-mm radius was 0.1% water soluble, and at the Buffalo-1 tower burst, debris of 1-cm radius had 0.01% water solubility. Silicate sand (SiO2) has a density of 1.54 grams per cubic centimetre, and comprises 80% of soil above CaCO3 rock at the Australian-British Maralinga test site. Silicate minerals are the most common in the Earth’s crust, forming the most rock and sand. (These fallout solubility data on Australian-British nuclear tests Antler, Mosiac and Buffalo-1 come from Porton Technical Reports in the U.K. National Archives. The British chemical warfare laboratory at Porton Down conducted fallout decontamination and solubility research at Maralinga and Monte Bello under contract to the Home Office Scientific Advisory Branch for civil defence, and the War Office for military research.)

Above: calcium oxide, -hydroxide, and -carbonate from Tewa coral reef burst, 1956. Coral sand (like chalk and limestone) is calcium carbonate, CaCO3, which dissociates into CO2 and CaO when heated to a temperature of 850 °C in the fireball. CaO melts at 2,570 °C, which must be reached for the core of the particle to be uniformly contaminated with fission products. The outside of the CaO core reacts with atmospheric moisture to form a calcium hydroxide layer during fallout: CaO + H2O -> Ca(OH)2.

Reaction of the outer surface of this calcium hydroxide layer, Ca(OH)2 with atmospheric CO2 at temperatures below 30 °C creates an outer shell of CaCO3 + H2O. About 38.5% by mass of particles in the 1956 Zuni coral surface burst test had surface contamination only, but 98.7% of the radioactivity was contained in uniformly contaminated particles. The fallout density for coral bursts ranged from 2.36 grams per cubic centimetre for Bravo to 2.46 for Zuni. The solubility in water for Bravo and Zuni fallout was 20%. Nearly complete solubility occurred in weak acid. These fallout particles disintegrated rapidly upon contact with water and formed colloidal suspensions, almost entirely trapped above the ocean thermocline.

Above: black magnetic fallout particle (magnetite) from Inca steel tower burst, 1956. The Redwing-Inca test was a 15.2 kt-bomb was fired on top of a 61-m steel tower (containing 165 tons of iron) over coral sand at Eniwetok Atoll. Magnetite (Fe3O4) particles formed, and the mixed coral and steel formed marbles of contaminated black dicalcium ferrite (2CaO.Fe2O3) with veins of uncontaminated calcium hydroxide. By measuring the ratio of calcium to iron in the fallout, the mass of coral converted into fallout was found to be 264 tons. Only the top 2 mm of the sand around ground zero was thus swept up by the afterwinds:

‘The fact that only a thin layer of sand was actually either vaporized or melted, even though in contact with the fireball… indicates that the thermal effects penetrate only superficially into solid material during the short duration of the very high temperatures. By computing the energy required to heat, decarbonate, and melt 264 tons of coral sand and to heat, melt and vaporize 165 tons of iron … 8.5% of the available radiant energy [i.e., 3% of bomb yield, because the radiant energy was 35% of the total energy of the explosion] was utilised for heating the tower and soil material.’ – Charles E. Adams and J.D. O’Connor, U.S. Naval Radiological Defense Laboratory, report USNRDL-TR-208, 1957, p. 13.

Above: typical glossy magnetic fallout particle, Upshot Knothole tower burst, 1953
The density of Upshot Knothole fallout from a detonation on a 91-m tall steel tower was 2.15 grams per cubic centimetre, a mixture of black magnetic iron oxide (magnetite, Fe3O4) from the steel tower and silicate glass from melted grains of Nevada sand. The particle core contains air bubbles and is a sand grain, melted into glass. The outer region contains the magnetite and the radioactive fission products. Studies at the 1957 tests Diablo and Shasta showed that steel tower shot fallout is 5% magnetite by mass and can be picked up with a magnet (U.S. Naval Radiological Defense Laboratory report USNRDL-466, 1961).

The salt slurry droplet from a Redwing seawater surface burst (detonation on a steel barge in Bikini Lagoon) was deposited in 80% humidity air. Its density is 1.4 grams per cubic centimetre and it contains salt crystals precipitated in supersaturated salty water. Obviously, in drier air the particles are smaller and denser because the water content of the particles falls due to evaporation. In 80% humidity air an equilibrium water content occurs because the salty droplets are hydroscopic (they form surfaces for condensation of airborne moisture, which at some diameter offsets the evaporation effect). The radioactivity solubility is 35% as ions or cations (ions with positive charge in solution), while 65% of the activity is trapped insoluble in fused tiny particles of dicalcium ferrite created from the steel barge and the coral sand ballast in the barge.

Decontamination of fallout

If the fallout is in soluble form (as for a detonation involving proximity to sea water), then the problems are at their worse because many of the fission products are present in the ionic solution and become chemically bound to surfaces. If the detonation occurs over a typical land surface which is about 50% or more silicate (e.g., typical sand), then the decontamination is easier because most of the activity is insoluble (trapped in the solidified spheres of glass). Dry fallout can be decontaminated by a range of activities from flushing it down storm drains with water hosing, to using normal mechanical street sweepers. Inclined roofs do not retain large fallout particles efficiently, simplifying decontamination of buildings. The efficiency of decontamination depends strongly upon the total quantity of fallout taken up into the mushroom cloud and stem, which is typically about 1% of the mass of material ejected from the crater in a surface burst, typically 100-300 tons of fallout per kiloton of yield.

For example, when decontaminating land surface burst fallout from portland cement concrete by fire-hosing, the fallout protection factor afforded by this decontamination is 25 for a fallout deposit of 100 g/m2, 50 for 330 g/m2, and 125 for 1,000 grams/m2. These deposits of 100, 330, and 1,000 g/m2 typically correspond to 1 hour reference gamma exposure rates of 300, 1,000 and 3,000 R/hr respectively. Hence the best efficiency for decontamination occurs where the danger is most severe. Where the fallout is very light, decontamination is less efficient because the smaller number of smaller sized fallout particles involved tend to quickly get caught or trapped in small crevices, cracks or surface irregularities, where water flushing is less effective. (These data are from Radiological Recovery of Fixed Military Installations, U.S. Army Chemical Corps Technical Manual TM-3-225 (1958). This fire-hosing method uses 4-cm diameter hoses, each crewed by 2-4 people, with 100 gallons/minute of water at 5 atmospheres pressure to decontaminate 700 m2/hour; fallout is flushed into underground drains to decay, so the radiation is safely absorbed below ground level.)

Nevada nuclear weapon test experience: dry fallout on paved areas 0.6-1.6 km from nuclear tests Sugar and Uncle in 1951 was successfully removed: ‘High-pressure water hosing was found to be the most rapid and effective … None of the tested procedures [including dry sweeping and vacuum cleaning] resulted in significant contamination of the operator’s protective clothing.’ – J. C. Maloney, Decontamination of Paved Areas (U.S. test report WT-400, 1952, Ch. 5). The contamination per unit area of vertical walls was only 0.3-10% of that on horizontal ground and roofs (Jangle Project 6.2, WT-400, 1952).

F. T. Underwood of the U.K. Home Office reported fallout adherence: over 90% of fallout particles exceeding 1 mm in diameter rolled or bounced off roofs with a 45-degree slope. But 95% of fallout particles less than 0.2 mm in diameter adhered to a 45-degree ceramic tiled roof. For a 45-degree roof slope, 90% of the retained fallout on 0.13 cm thick PVC (glued to the roof) was removed by just 1 litre/m2 (0.1 cm of rain). Without PVC, fallout grains roll into, and lodge in, small pits and crevices (reports CD/SA-103 and CD/SA-125, 1961-5).

Experience of fallout in unprotected civilian areas of America was obtained after four 1953 Nevada shots on 91-m high towers:Annie, Badger, Simon, and Harry. The 1957 U.S. Congressional Hearings, The Nature of Radioactive Fallout and Its Effects on Man, pp. 231-2, show that Nevada staff washed vehicles on highways where the infinite time dose exceeded 5 R (using the t-1.2 formula, Dinfinity = 5RT, where R is dose rate at start time T after burst).

The highest public fallout is listed as being 97 km downwind from the Harry test, where the peak outside dose rate was 1 R/hr on Highway 93 at 2 hours after burst: ‘The ratio of dose rate readings on the outside of the car to inside varied from unity to about 4/1 … One bus read 250 mR/hr outside and an average of 100 mR/hr inside with a high inside reading over the rear seat of 140 mR/hr at H + 8.75 hours.’ At St George, Utah (210 km downwind), the Harry fallout reached 0.42 R/hr at 3.75 hours with a measured peak air concentration at the same time of 154,000 Bq/m3.. The 4,500 inhabitants were requested by radio to stay indoors for two hours to avert skin contact.

Decontamination of Farms: roads, paved areas, building surfaces, vehicles, aircraft and ships can be decontaminated by water hosing. For fields, single-pass deep-ploughing to 20-25 cm depth (3,250 m2/hour using an old 125 horse-power tractor with a 3-share plough) reduced the above-ground fallout gamma radiation by an average factor of 6.7 (U.S. Army Chemical Corps technical manual TM-3-225, 1958).

If needed, fallout can be deep-ploughed to a depth below the roots of the crops to prevent root uptake, or the long-term agricultural uptake of Sr-90 and Cs-137 can simply be dramatically diluted by adding calcium and potassium salts to contaminated soil. About 2.6% of the Earth’s crust is potassium, which minimises Cs-137 uptake, but there is often a shortage of calcium so Sr-89 and Sr-90 can contaminate food. However, in chalky, limestone or coral soils there is plenty of calcium (which blocks Sr-89 and -90 uptake), but little potassium, so Cs-137 is important. Adding potassium chloride to the coral soil of Bikini Atoll (scene of 76.8 Mt of tests) in the 1990s reduced the Cs-137 in coconuts from 3,700 Bq/kg to 185 Bq/kg. Growing crops with low calcium content reduces the uptake of Sr-89, -90 (potatoes contain only 1 mg of calcium per 10 calories).

City decontamination: Britain planned decontamination by fire-hosing residential areas where the 1-hour reference gamma dose rate was 500-3,000 R/hr (Home Office report SA/PR-97, 1965, originally secret). At lower levels, there are few casualties indoors anyway (200 R producing a casualty), while higher levels expose decontamination crews to excessive doses even 5 days after detonation, so evacuation is then a better option. Decontamination is feasible at 1-5 days after detonation, when a 1-hour outdoor dose rate of 500-3,000 R/hr has decayed to 10 R/hr. Decontamination crews restricted to areas below 10 R/hr cannot get more than 10 x 8 = 80 R in an 8 hour shift.

The three key stages during radiological recovery after first aid, rescue and fire spread prevention: (1) evacuation of people with inadequate shielding from heavy fallout areas; (2) sheltering for 1-5 days in the part of the house furthest from the roof and outside walls, with as much mass around the ‘inner refuge’ as possible, and staying indoors as much as possible for a month, and (3) outdoor decontamination.

Washing skin removes 97.5% of fallout with a diameter of 0.02 mm, and removes 100% of fallout of 0.1-mm diameter or more. For clothes, 90% of the fallout on denim overalls is removed in 5 minutes by a washing machine (100 revolutions per minute, 1% detergent), for particle diameters over 0.01 mm. (Reference: E. Neale and E.H. Letts, Radiological Decontamination: Removal of Dry Fallout from Skin and Clothing, U.K. Chemical Defence Experimental Establishment, report PTP-R-16, 1958.)

Internal fallout contamination of humans: inhalation of fallout in Britain from the American and Russian tests of 1958 peaked at 3.7-Bq/day of beta emitters between January-June 1959, when the total fallout intake from food was 120-Bq/day. The maximum concentration of plutonium in the air was lower than natural radon-222. For Sr-90, the intake in Britain in 1959 was 0.33-Bq/day from food, 0.015-Bq/day inhalation, and tap water contained 0.016-Bq/litre (reference: The Hazards to Man of Nuclear and Allied radiations: Second Report to the Medical Research Council, H. M. Stationery Office, London, 1960).

The initial danger is due to eating fallout: even after years of fallout from nuclear tests, 80% of the Sr-90 in milk in Britain during 1958 was from cows eating fresh fallout deposited on the grass and soil, and only 20% was due to chemical uptake by roots and ingestion of older fallout in the soil. (J.D. Burton et al., Nature, Vol. 185, 1960, p. 498.)

Decontamination of water and milk: boiling water does not remove fallout or affect radioactivity. Filtering removes fallout particles, but it is the dissolved, soluble radioactivity that causes the major ingestion problem. Activated charcoal cartridges or ion exchange softens tap water by removing calcium carbonate ions, and also remove dissolved fission products. Distillation also makes water safe. Milk is decontaminated by filtering with on-exchange resin, but this also removes the calcium from the milk.

On 7, 11, 14 and 17 July 1962 low-yield nuclear weapons were detonated near ground level in Nevada, and the 100-kt Sedan Nevada test occurred on 6 July. Fallout on grass 560 km downwind in Salt Lake City was relatively soluble, so milk contained enough I-131 to give a total I-131 intake from milk of 1,370-Bq. Families switched to using milk powder. Out of 759 milk producers in the area, 285 switched their cows from pasture to uncontaminated dry feed, and 211 stopped selling milk but instead used it to make long-life products like cheese, which outlive I-131 (which has a half-life of only 8 days).

After Britain’s Windscale nuclear accident of October 1957, the concentration of I-131 in contaminated milk was 500 times higher than that in tap water from reservoirs in the same areas. Ion-exchange interaction of soluble nuclides with soil or rock slows down the migration of dissolved radioactivity in groundwater and surface rain run-off. It was 30 days after the Chernobyl reactor accident in 1986 when tap water, obtained from a river in the nearby city of Kiev, attained a peak activity of 370-Bq/litre, which returned to natural background within a year. The 1957 U.S. Congressional Hearings on fallout, p. 233, shows that the maximum contamination of tap water 3 days after any 1953 Nevada nuclear test was only 44-Bq/litre (at Bunkerville, Nevada, where the gamma outdoor infinity dose was 7 R), compared to 3,200-Bq/litre in an irrigation canal.

The ocean food chain: concentrates iron (Fe) and zinc (Zn) in clams, fish and fish-eating birds. But soil usually contains plenty of soluble iron and zinc that dilutes their uptake to insignificance. In oceans, natural potassium and calcium similarly dilute the uptake of cesium-137 and strontium-90, respectively. But oxygen dissolved in the ocean soon oxidises soluble ferrous (2+) iron into insoluble ferric (3+) iron, which precipitates as a solid. Soluble iron, zinc and cobalt are extremely rare in seawater and are therefore taken up in ocean food chains. A month after the 1.69 Mt Nectar shot at Eniwetok in 1954, 95% of the activity of fish was Fe-55, 3.1% was Zn-65, and the rest cobalt. The activity in sea birds at Bikini, in 1954-6, was mainly Zn-65. Fe-55 gave 73.5% of the activity of a clam kidney at Eniwetok, 74 days after the 1.85 Mt 1956 Apache shot (cobalt-57, -58, and -60 contributed 9.6, 9.2, and 1.8%; fission products gave 3.5%). Zn-65 in fish at Bikini, 2 months after 1956 Operation Redwing, gave 35-58% of the activity, Fe-55 gave 15-56%, and cobalt gave the rest (U.S. report UWFL-51, 1957).

The fallout uptake after the 10.4 Mt Mike land surface burst in 1952 were measured at and near the islands of Rigili, Bogombogo-Bogallua, Engebi, Aomon-Aaraan, and Runit, in Eniwetok Atoll (U.S. test report WT-616, 1953). The activity per gram of muscle tissue of rats was similar to that in their lung tissue, so ingestion rather than inhalation was the mechanism of internal contamination by fallout. The average ratio of beta activities collected at 7 days and measured at 30 days, to the adjacent land gamma dose rate at 1 hour, (Bq/kg)/(R/hr), was 1.8 for lagoon water, 8,800 for plankton, 15,000 for land plants, 2,800 for crab muscle, 120 for the muscle of plankton-eating fish, and 58 for rat muscle (DASA-1251, 1963, was used for gamma dose rates). Half the water is flushed out of Eniwetok lagoon (which has a mean depth of 48 m) in 15 days.

Farm and food decontamination after fallout is particularly important. In 1960-1, Kendal D. Moll of Stanford Research Institute showed in Post-Attack Farm Problems that while a 400 Mt Russian first-strike on American military bases would kill 2% of the population (assuming a fallout protection factor of 20), farm food output falls by 10%. For 19,000 Mt, he found that a population reduction by 12% occurs with a 65% fall in food output. Norman Hanunian stated in his 1966 RAND Corporation report Dimensions of Survival, p. 33: ‘the possible post-attack state of the farm sector … constitutes the greatest threat to national viability.’

It is worth summarizing some of the more reliable Nevada nuclear test empirical data for surface bursts JOHNIE BOY (0.5 kt, 1962), SUGAR (1.2 kt, 1951) and SMALL BOY (1.65 kt, 1962) which is tabulated on page 61 of Hillyer G. Norment’s DELFIC report DNA 5159F-1, 1979 (his data for Pacific shots KOON and ZUNI are from error filled reports and are both obsolete). At 1 hour after burst, a measured gamma dose rate on point-source-calibrated survey meters of 100 R/hr at 1 m height over contaminated Nevada desert (corresponding to an ideal smooth plane dose rate of roughly 200 R/hr for a survey meter which isn’t partially shielded by its own batteries and by the person holding it) occurred in an elliptical belt 0.25 km wide extending 2.73 km downwind from 0.5 kt JOHNIE BOY, 0.49 km wide extending 3.74 km downwind from 1.2 kt SUGAR, and 0.84 km wide extending 5.66 km downwind from 1.65 kt SMALL BOY. It should be noted that the exact depth of burst has a greater effect on the dangerous levels of fallout than the wind velocity. The wind doesn’t affect the fallout dose rates very much, because if you double the wind speed, the same amount of fallout gets deposited over twice the area with therefore only half the concentration than for the lower wind speed, so the increase in downwind distance reached by any given fallout particle is largely offset by the fact that the particles are spread out over a greater tract of ground. Thus, in practice there is relatively little wind effect on fallout, apart from obviously determining the directions which the fallout plumes travel.

However, the fallout contour data show a great dependence on the exact depth or height of burst. Very shallow depths of burst greatly increase the cratering efficiency, producing more intense close-in fallout contours due to the extra activity carried by large particles contaminated at early times by the cratering ejecta mechanism. For example, the 1000 R/hr contour at 1 hour extended 1.38 km downwind and 0.26 km in width after the JOHNIE BOY 0.5 kt shot at 0.584 m depth, but such dose rates were confined to the crater in the 1.2 kt SUGAR burst detonated 1.067 m above ground!

Perhaps the best set of data comes from the 1962 SMALL BOY shot (1.65 kt Nevada burst at 3.05 m height above ground):

Above: Dr Carl F. Miller’s fallout model from 1963 is based on a semi-empirical analysis of the Pacific nuclear test fallout patterns from CASTLE and REDWING nuclear test operations in 1954 and 1956, in combination with a theoretical analysis of all the physics and chemistry of the fallout mechanism itself. (C. F. Miller, Fallout and Radiological Countermeasures, Stanford Research Institute, January 1963, vol 1 – AD410522, vol. 2 – AD410521.) Miller’s model predicts an earliest fallout arrival time of 4W0.2 minutes after burst, where W is the total weapon yield in kilotons. Hence, fallout under the mushroom cloud begins to arrive at 16 minutes after burst for 1 Mt, 22 minutes after burst for 5 Mt, and 30 minutes after burst for 25 Mt. (These data are from the DCPA Attack Environment Manual, Chapter 6, What the Planner Needs to Know About Fallout, U.S. Department of Defense, Defense Civil Preparedness Agency, report CPG 2-1AG, June 1973, Panel 29.)

Above: the earth penetrator warhead destroys hardened underground targets by ground shock and cratering with a low fission yield and can dramatically reduce fallout by trapping fission products deep within the crater ejecta layer. (The data for SEDAN is scaled back to 1 hour after burst using the decay rate curve, and thus exaggerates the radiation levels which occurred far downwind when the arrival time was greater than 1 hour.)

Above: Nevada nuclear test data shows the effect of burial on dose rate contours. Very shallow depths can enhance local fallout, but greater depths reduce it. Notice that the 100 R/hr contour at 1 hour after burst extends several km downwind for 1.2 kt surface or shallow detonations in dry soil, but much less than 1 km downwind for the bursts of 0.42-31 kt yields at depths of 34-110 m in hard rock.

The posts here are supposed to be particularly important information. However the arrangement of the information is haphazard and I’m compiling a book on the application of science to nuclear reactions, with chapters ranging from the big bang evidence to nuclear forces, nuclear explosions, and all of the effects produced. This will be available freely as PDF page files on my domain http://quantumfieldtheory.org/ as soon as possible. It will be edited more carefully (and will of course be better organized) than this blog, and will contain far more detailed information on each topic.

Update:

Articles by Dr Miller and others in the August 1958 Journal of Colloid Science:

“Calculations are made of the gamma radiation rates for the 13 radioisotopes contributing the major portion of gamma radiation from a deep underwater nuclear detonation. These calculations are carried out for 14 different times after the burst ranging from 40 min to 3 years. The gamma emitters include activities induced in sea water and possible bomb components as well as fission products.”

“The expected general composition of fall-out from a nuclear detonation in a homogeneous liquid medium (sea water) is discussed, Simplified contaminants each containing a single fission product element and sea water applied to a painted surface were decontaminated by water washing. Decontamination as a function of initial level or surface density of most of the FP elements used was found to follow the modified Freundlich relationship R = aI/sup n/ in which I is the initial level, R is the level remaining after decontamination, and a and n are constants for each element.”

“The decontamination of San Francisco harbor bottom soil, Nevada test site soil, and a commercial clay from a paint surface was done with stirred and sprayed water, The surface density of soil remaining after decontamination was found to depend on the initial condition according to the equation, R/sub m/ = R/ sub M/(1-e/sup -ay/) in which R/sub M/ is a constant related to tbe mean particle size remaining, a is a constant related to the mean particle size and density of the deposited soil, and y is the surface density of the initial deposit. Estimates are made for the gamma radiation intensity over the contaminated and decontaminated surfaces for the case in which the surface area is large and the soil is fallout from a surface land atomic detonation.”

10 comments:

There is a fairly extensive list of Dr Carl F. Miller’s reports on the U.S. Department of Energy “Opennet”, https://www.osti.gov/opennet (these are listed below, straight from the search, note some reports are duplicated in the list several times).

Dr Miller’s 11 July 1957 U.S. Naval Radiological Defense Laboratory report “Gamma Decay of Fission Products from the Slow-Fission of U235″, USNRDL-TR-187 and his related report on 4 August 1958 with P. Loeb, “Ionization Rate and Photon Pulse Decay of Fission Products from the Slow-Neutron Fission of U235″ (USNRDL-TR-247), were the first theoretical gamma dose rate decay curve from fallout fission products.

The results from these reports were discussed during the U.S. Congressional Hearings of 22-26 June 1959 before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, “Biological and Environmental Effects of Nuclear War” (pages 77, 113ff, 181, 187, and 189-223).

See also the U.S. Congressional Hearings before the Special Subcommittee on Radiation of the Joint Committee on Atomic Energy, May 1959, “Fallout from Nuclear Weapons Tests”, page 1969.

Dr Miller’s research overturned the reliance on the t^{-1.2} decay rate, by showing that for times beyond 100-200 days after the explosion the real radiation level falls below that predicted by the t^{-1.2} decay law used in the 1950 and 1957 editions of Glasstone’s “Effects of Atomic/Nuclear Weapons” book.

Dr Miller, apart from this theoretical work, also did empirical correlation and analysis of fallout decay rates measured from fallout collected after nuclear tests, in his report: “Analysis of Fallout, Part II, Decay Characteristics of Radioactive Fallout”, USNRDL-TR-221, 9 May 1958.

Dolan analysed two situations: fission weapons using U235, and thermonuclear weapons using U238, in each case allowing for fractionation (loss of most Kr and Xe fission fragment decay chains from the hot fireball and their near absence in local fallout due to depletion from large, fast falling particles), and neutron induced activities U237, U239, Np239 and Np240.

Dolan concluded that the fallout from both fission and thermonuclear weapons decayed at t^{-1.23} for 1 hour to 100 days, to within an accuracy of +/- 9% for fission weapons and +/- 25% for thermonuclear weapons. Beyond 100 days, the true radiation level decreases faster than this formula and in the interval of 3-6 years after a nuclear explosion the dose rate is about 10 times lower than predicted by t^{-1.23} (if extrapolated from times less than 100 days). Beyond 10 years, the contribution of Cs-137 (30 years half-life) predominates unless there is a lot of neutron induced Co-60 (5.3 years half-life).

A slightly revised version of the curve for a thermonuclear weapon (using better fractionation and neutron induced activity estimates than Dolan used) was incorporated into the 1962/64/77 editions of “The Effects of Nuclear Weapons”.

Dr Miller’s reports (titles listed on Opennet):

INTRODUCTION TO LONG TERM BIOLOGICAL EFFECTS OF NUCLEAR WAR MILLER, C.F. ; LARIVIERE, P.D. NV0004820

In addition to the decontamination, shielding by existing buildings (even if doors and windows are broken by air blast, allowing ingress of fallout to the same contamination density as outdoors) is useful for reducing dosage before the dose rate has decayed enough to allow lengthy decontamination efforts.

This is because the majority of the dose comes to you horizontally from an average radius of 15 metres around you on smooth contaminated terrain. Hence, relatively little dosage is coming from the fallout directly under your feet and nearby. The long range of fallout gamma rays in air means that 50% of the gamma dosage comes from distances beyond 15 metres from you, and 50% from fallout deposited within 15 metres radius. Typically 85% of this is direct gamma radiation, and only about 15% is air scattered gamma rays. When you calculate the average angle that gamma rays are coming to you from, it is very close to horizontal because of the large distances from which the majority of the dose (direct gamma rays) originate.

Hence, if you went on to contaminated ground and built a house (without decontaminating the ground below you at all), you would still get very good protection against gamma radiation even though the floor below you was contaminated: the walls of the building would be attenuating the majority of the gamma ray dose which comes from large distances almost horizontally (not vertically up at you). So even if the contamination density on the floor (becquerels per square metre) is the same indoors as outdoors (due to the roof being ripped off by blast or whatever), any surviving outer walls would provide you with useful gamma radiation shielding against the lateral exposure to long range, almost horizontally-travelling direct gamma rays.

In reality, most of the fallout area where protection is needed is outside the severely blast damaged area, so the majority of buildings which require fallout shielding will not be that badly damaged. Broken doors and windows will let some fallout in, but since fallout grains are quite large (like sand) most will not ingress very far and the average contamination density on the floor of a building with broken windows/doors will be small compared to that outdoors.

Fallout protection factors

The protection factor of any building is greatest near the middle of the floor furthest from the roof, i.e., well away from fallout that is mainly located beyond outside walls and on the roof. Ingress of fallout within a building makes little difference, since the fallout doses come from the major amounts of contamination on large contaminated areas, not small quantities of fallout. This is illustrated by the fact that a person standing on uniformly contaminated terrain doesn’t receive all their dose from the nearby fallout they are standing on, instead 50% of the gamma rays come from fallout deposited over 15 metres away. The minimum protection factor in a building occurs near windows at outside walls, and on the floor below a contaminated roof.

Caravans have a protective factor of 1.4-1.8, single storey modern bungalows have a protection factor of 5-6, while brick bungalows have a protective factor of 8-9. British brick multi-storey buildings have protection factors of 10-20, while British brick house basements have protective factors of 90-150. These figures can easily be increased by at least a factor of 2-3 by making a protected ‘inner core’ or ‘refuge’ within the building at a central point, giving additional shielding.

The most important for emergency use (where rapid protection is desirable) are the “car over trench shelter” (dig a trench the right size to drive your car over, putting the excavated earth to the sides for added shielding, then drive your car over it), “tilt up doors and earth” shelter (if your house is badly damaged, build a fallout shelter against any surviving wall of the house by putting doors against it and piling earth on top in accordance to the plans), and the “above ground door-covered shelter” (basically a trench with excavated earth piles at the sides, doors placed on top, then a layer of earth piled on top of the doors). All these shelters can be constructed very quickly under emergency conditions (in a time of some hours, e.g., comparable to the time taken for fallout to arrive in the major danger area downwind from a large nuclear explosion).

“This manual is designed to assist local civil defense organizations prepare plans consistent with the changing strategic conditions of the seventies. The Defense Civil Preparedness Agency is moving into a new program of ‘all-hazards, all-contingencies’ planning which will involve developing a crisis-oriented evacuation capability. This capability will increase the survivability of the population in the event of a nuclear attack and will be a counter against certain ‘nuclear blackmail’ threats. Planning for the development of shelter capabilities for either an ‘in-place’ or evacuated posture will require an ability to rapidly build large numbers of new expedient shelters in addition to upgrading existing fallout shelters. Detailed step-by-step instructions and pictorial design drawings of fifteen expedient shelters are included in the Appendices. The instructions and drawings for any of these shelters can be preprinted by local C.D. organizations for rapid dissemination in a crisis.”

Kearny of course went on to write the Oak Ridge National Laboratory publication “Nuclear War Survival Skills”, although in some ways that is more controversial (it doesn’t include nuclear test data to justify all the claims made) and might be simply far too lengthy for most people to read in an emergency, http://www.survivalring.org/pdf/nuclearsurvivalskills.pdf

I’ve just found a very informative 10 page article by Dr Carl F. Miller, “Physical Damage from Nuclear Explosions”, published on pages 1-10 of the August 1963 book “Ecological Effects of Nuclear War” edited by G. M. Woodwell, the book being the Proceedings of a Symposium Sponsored by the Ecological Society of America at the Thirteenth Meeting of the American Institute of Biological Sciences, Amherst, Massachusetts, Brookhaven National Laboratory, report BNL 917 (C-43), AEC document TID-4500, 41st ed, and it is available online in its entirity for download at:

This contains vital information which is not included in any edition of “The Effects of Nuclear Weapons”, for example the contamination factors for plants measured at several nuclear tests (which is vital for determining what the hazards to growing crops are after fallout occurs, what decontamination is needed, etc.).

The key declassified report by Dr Carl F. Miller is USNRDL-466, which since this post was written (which links to a copy of that report on a U.S. government run server), has been removed from the U.S. government document collection or the link has become corrupted. Hence the link in this post to USNRDL-466 does not work any longer.

An alternative server also hosts that crucial report by Dr Miller here:

Table 11 (on page 41 of the original document) contains all of the originally Secret – Restricted Data on neutron induced activities U-239/Np-239, U-237, and Np-240 in the fallout from 13 different key Jangle, Castle, Redwing and Plumbbob fallout producing tests.

Notice that i(1) on the top line of the table data is the reference 1 hour dose rate assuming 1 atom/fission, so that allows you to work out the atoms/fission ratios from the 1 hour dose rates given in that table.

E.g., the Sugar and Uncle shots of Jangle in 1951 both produced 1-hour reference dose rates of 0.106 units due to U-239, which itself would produce 0.1799 units if there was 1 atom/fission of U-239 produced.

Hence, Sugar and Uncle both produced 0.106/0.1799 = 0.59 atoms/fission of U-239 and Np-239 (ignore the data given in the table for Np-239 because that is for the actual Np-239 atoms per fission created by 1 hour, not the total Np-239; since Np-239 is created from the decay of U-239, the total amount of Mp-239 produced is identical to the amount of U-239 produced, but because U-239 has a half life of 23.5 minutes, only 83% of the Np-239 has actually been formed within 1 hour of detonation).

As the table shows, only thermonuclear weapons produce significant quantities of U-237.

It is also worthy of note that the fission bomb tests Diablo and Shasta of Plumbbob in 1957 both produced only 0.10 atom/fission of U-239/Np-239, which is only about one-sixth of the production in the 1951 Sugar and Uncle tests.

The reason is that the 1951 tests Sugar and Uncle were old-fashioned implosion bombs with thick U-238 neutron “reflectors” that (instead of simply reflecting neutrons back) captured a large proportion of neutrons emitted from the core, whereas the 1957 tests Diablo and Shasta did not employ U-238 as a thick neutron reflector. The smaller amounts of U-238 contained in Diablo and Shasta was present in the highly-enriched uranium that was used in the composite uranium-plutonium cores that were in use at that time.

Notice also that Castle-Bravo produced 0.56 atoms/fission of U-239/Np-239, 0.10 atoms/fission of U-237, and 0.14 atoms/fission of Np-240, according to Dr Miller’s secret data.

Japanese investigators tried to measure the capture/fission ratios from the Castle-Bravo fallout that landed on the “Lucky Dragon No. 5″ which was 100 miles downwind of the detonation (it was just north-west of Rongelap when fallout arrived).

To avoid secrecy, Dr Miller quoted the (unclassified) Japanese findings in his unclassified 1963 “Fallout and Radiological Countermeasures” SRI report and also in his 1964 SRI report “Biological and Radiological Effects of Fallout from Nuclear Explosions”: the data from the Japanese physicists suggest a figure of 0.30 atoms/fission for U-239/Np-239 and 0.15 atoms/fission for U-237.

These figures are wrong: the first is too low and the second is too high. You can’t chemically separate small quantities of these nuclides because they are quite similar chemically, so you can’t distinguish the beta particles, only the gamma ray energies using a crystal and scintillation counter. The problem of accurate determination comes down to the quality of the equipment and the quality of the samples of the fallout. The fallout that had been subjected to spray and wind on the decks of the “Lucky Dragon No. 5″ for two weeks on the voyage back to Japan was not idea, and nor was the calibration of the instruments which the Japanese physicists used.

The American data is far more reliable. In addition, the Japanese physicists did not know about fission product fractionation (see table 8 on page 35 of the declassified report by Dr Miller for fully corrected detailed fractionation data downwind from the Redwing 1956 tests), which reduced the accuracy of their determination of capture atoms/fission. This is because, in order to determine the number of say U-239 atoms/fission, you need to determine not only the number of U-239 atoms in your sample, but also the number of fissions. If you try to determine the number of fissions by measuring the number of Sr-90 atoms present and using the production ratio of Sr-90 on standard “M” shaped fission fragment abundance graphs, you will underestimate the number of fissions, because Sr-90 is depleted from local fallout due to the fireball temperature. The correct way to work out the amount of fission in a sample is to determine the number of atoms of something that is not fractionated, such as Nb-95 (the Americans originally in the 1950s used Mo-99 as the reference nuclide, switching to Nb-95 in the 1960s because it is more abundant in fallout, and is thus easier to measure with greater accuracy).

One other measurement of interest for the 1956 Redwing series is in the report by M. Morgenthau, H.E. Shaw, L.M. Hardin, R.C. Tomkins, and P.W. Krey, Preliminary Report, Operation Redwing, Project 2.65, Land Fallout Studies, U.S. Armed Forces Special Weapons Project, Sandia Base, Albuquerque, ITR-1319, January 1957: the Redwing-Lacrosse 40 kt test produced 0.2 atom/fission of Np-239.

In his 1959 report The Decontamination of Surfaces Contaminated with Fallout from Nuclear Detonations at Sea, U.S. Naval Radiological Defense laboratory, report USNRDL-TR-329, Dr Miller makes it clear that although Np-239 and U-237 can contrubute 50% of the gamma dose rate some days after a thermonuclear explosion, neutron induced activity from Na-24 in sea water is trivial by comparison.

Dr terry Triffet and Philip D. LaRiviere support this with detailed tables of neutron induced activity from a variety of different thermonuclear weapons (clean and dirty fission yields) tested during Operation Redwing in 1956, in their report Characterization of Fallout, weapon test report WT-1317 (1961):

Corrections in bold to the following paragraph taken from the second-to-last comment above:

“These figures are wrong: the first is too low and the second is too high. You can’t chemically separate small quantities of these nuclides because they are quite similar chemically, and you can’t distinguish them on the basis of the emitted beta particles, only by their gamma ray energies using a sodium iodide crystal and scintillation counter. The problem of accurate determination comes down to the quality of the equipment and the quality of the samples of the fallout. The fallout that had been subjected to spray and wind on the decks of the “Lucky Dragon No. 5″ for two weeks on the voyage back to Japan was not ideal, and nor was the calibration of the instruments which the Japanese physicists used.”

As another update, there is another very important report by Dr Carl Miller available online as a PDF file now:

Dr Carl F. Miller, Biological and Radiological Effects of Fallout from Nuclear Explosions, Chapter 1: The Nature of Fallout and Chapter 2: Formation of Fallout Particles, Stanford Research Institute, Menlo Park, California, SRI Project No, IMU-4536, March 1964, 89 pages with excellent illustrations of fallout from nuclear tests and tables of fallout particle radionuclide solubility (tables 2.1, 2.2 and 2.3), quantitative uptake of various fallout radionuclides in rabbits 20 days after the Plumbbob-Smoky nuclear test in the Nevada in 1957 (table 2.4), fission product yields for seven types of fissile material and nuclear weapon designs (table 2.5), and the effect of fireball heat in fractionating the deposition of fission products upon the fallout particles which fall out of the fireball at different fireball temperatures – e.g. the biggest fallout particles that land near ground zero fall out of the fireball while it is still extremely hot, so they contain virtually no volatile fission products which have yet to start condensing in the fireball, but smaller particles fall out of the fireball after it has cooled and so they are plated with more volatile fission product decay chains (table 2.9 shows the experimentally observed fission product fractionation range in deposited and cloud fallout samples for four different Redwing tests A, B, C and D, which are identified in the declassified WT-1317 report as Redwing shots Zuni, Tewa, Flathead and Navajo, respectively; note that WT-1317 also gives the absolute distances of the various collection stations from ground zero, allowing fractionation to be correlated to distance from ground zero and to median fallout particle size since the relation of particle size to distance is a simply determined by the measured fallout time of the peak dose rate at each location):

Abstract : The major purpose of this report is to outline and discuss these physical processes and the important parameters on which they depend. The data, data analyses, data correlation schemes, and discussions presented here are organized to emphasize size basic principles so that an appropriate methodology can be applied in evaluating the radiological consequences of nuclear war. An explosion of any kind, detonated near the surface of the earth, causes material to be thrown up or drawn into a chimney of hot rising gases and raised aloft. In a nuclear explosion, two important processes occur: (1) radioactive elements, which are produced and vaporized in the process, condense into or on this material; and (2) a large amount of non-radioactive material, rises thousands of feet into the air before the small particles begin to fall back. This permits the winds to scatter them over large areas of the earth’s surface. Thus, when the particles reach the surface of the earth they are far from their place of origin and contain, within or on their surface, radioactive elements. Whether they are solid particles produced from soil minerals, or liquid (salt- containing) particles produced from sea water, they are called fallout. The composition of fallout can be described in terms of two or three components. One is the inactive carrier; this consists of the environmental material at the location of the detonation and is the major component in a near-surface detonation. The second component includes all the radioactive elements in the fallout.

I want to publish the review that the British Home Office Scientific Advisory Branch did of Dr Carl F. Dr Miller’s 1963 Stanford Research Institute report “Fallout and Radiological Countermeasures”. It shows just how important that report was for planning in this country. I read that review around 1992. Later I bought Dr Miller’s report from NTIS in microfilm print-out. It is the key report, the only calculation of the actual mass of fallout produced by a surface burst, the fractionation of the different products on the fallout as it condenses while the fireball cools, and the effects of fractionation on the decay rate and decontamination effectiveness. So it answered all the concerns and questions the British Home Office had about fallout and enabled them to formulate their civil defence planning against fallout with a lot more confidence than they would otherwise have had, which eventually led to the U.K./ civil defence assault against Soviet funded WPC propaganda in 1980. The refusal to give in to Soviet propaganda and intimidation caused the Soviet union to go financially and then politically bankrupt (Gorbachev had to cut military spending when it went militarily bankrupt), and they were already morally bankrupt.

I gather from the reports which I read that when Dr Miller moved from NRDL to SRI around 1960, Dr Edward C. Freiling came in to NRDL from outside and took over Miller’s former position at NRDL. Freiling initially made a complete mess of the fractionation analysis, publishing a paper in Science journal in 1961 which added confusion by plotting the data in a useless way (Miller corrects Freiling’s data in his 1963 report, and in subsequent reports on fractionation Freiling used Miller’s 1963 study, citing it). I think the decision was taken to close down NRDL around 1969 when the fractionation question had been sorted out and the fallout from surface bursts was fully understood. To my mind, the fact that Dr Freiling tried falsely to deal with fractionation by an empirical correlation scheme instead of working out the mechanisms for the fission product separation in the fireball, indicates that Dr Miller’s model for the mechanisms was unique and extremely important, and probably would not have been done properly by others if he hadn’t been so motivated from his field experience of collecting and analyzing fallout.

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6/20/2011
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Race Realism

‘Man is a mammal and subject to the same biological laws as other animals. All animals, including Man, have inheritable behavioural traits. The concept of complete environmental plasticity of human intelligence is a nonsensical wishful-thinking illusion.’

From titans to Lemmings

“The time for talk has ended, only course of action open to us is WAR!”

"The time for talk has ended, only course of action open to us is WAR!"

The essential American soul is hard, isolate, stoic, and a killer. It has never yet melted. — D.H. Lawrence

Ayers’ Plan to Kill 25 Million Americans
Larry Grathwol, Weathermen, William Ayers, Communism, History
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“The most effective informer the F.B.I. ever placed among the Weathermen” (NY Times) Larry Grathwol describes how William Ayers and other Weather Underground leaders cheerfully planned to deliver the United States to foreign occupation, and proposed to murder 25 million Americans.

Grathwohl: I brought up the subject of what’s going to happen after we take over the government. You know, we become responsible for administrating, you know, 250 million people. And there was no answer. No one had given any thought to economics. How are you going to clothe and feed these people?

The only thing that I could get was that they expected that the Cubans, the North Vietnamese, the Chinese and the Russians would all want to occupy different portions of the United States. They also believed that their immediate responsibility would be to protect against what they called the counter-revolution. And they felt that this counter-revolution could best be guarded against by creating and establishing re-education in the Southwest where we would take all of the people who needed to be re‑educated into the new way of thinking and teach them how things were going to be. I asked, “Well, what is going to happen to those people that we can’t re‑educate, that are die-hard capitalists?” And the reply was that they’d have to be eliminated and when I pursued this further, they estimated that they’d have to eliminate 25 million people in these re‑education centers. And when I say eliminate, I mean kill 25 million people. I want you to imagine sitting in a room with 25 people, most of whom have graduate degrees from Columbia and other well-known educational centers and hear them figuring out the logistics for the elimination of 25 million people and they were dead serious.

Bring it on! WE WILL FIGHT YOU, WE HAVE BEEN MAKING BOMBS AND BUYING LEGAL AND ILLEGAL WEAPONS FOR YEARS, AND WHEN THE TIME COMES MY FELLOW PATRIOTS AND MYSELF, WE WILL TAKE TO THE STREETS, YOU WILL HAVE TO KILL US TO TAKE THIS NATION, BRING IT!!